In The Significance of Consciousness, Charles Siewert argues
that "phenomenal consciousness," the subjective feel
or character of conscious experience, is the most significant
aspect of our mental lives, and, what's more, many consciousness
researchers do not adequately account for phenomenal consciousness
in their theories. The book is a complex and sometimes difficult
work of philosophical investigation, and its style is often hard
to penetrate. But Siewert's main points can be succinctly distilled,
and they challenge those investigating the mind to thoroughly
explain the role of phenomenal consciousness in our lives.

The book opens with a defense of what Siewert calls "the
first-person approach to consciousness" (10). Consciousness
is known "from the inside" in a distinctly first-person,
subjective manner. This knowledge is not infallible or beyond
challenge, but, Siewert argues, unless we have good reason to
doubt the deliverances of first-person knowledge, we should respect
it. Siewert charges that many consciousness researchers ignore
this advice in the course of their investigations, and thus deny
or seriously downplay the importance of phenomenal consciousness.

Siewert develops and defends this claim by employing a variety
of thought experiments that isolate phenomenal consciousness,
and arguably show that many theories of consciousness "neglect"
(to use Siewert's favored term) the phenomenon. Siewert positively
describes phenomenal consciousness as what is "shared by
silent speech, other imagery, and sensory experience" (148),
but he also picks out the idea in the negative, as that quality
lacking in the neurological condition known as "blindsight."

Blindsight is a well-documented neurological deficit that can
occur when there is damage to the visual cortex. Subjects claim
they can't see anything in the damaged portion of their visual
field, but they are substantially better than chance at guessing
what is present there. They can identify the form, motion, orientation,
and perhaps the color of test stimuli, but they do not make these
judgments unless prompted to guess by investigators. The condition
suggests that a large amount of visual processing goes on in the
absence of consciousness, and many researchers have focused on
this result to craft their theories.

Siewert proposes that we imagine a blindsight subject who can
use the information gleaned from the blind field without being
prompted to guess, by "self cueing." Next we are to
imagine a subject with badly degraded but conscious blurry vision
who is able to make exactly the same sorts of discriminations
as our imaginary self-cueing blindsighter. Both subjects will
be able to make the same discriminations and arguably will behave
in the same way. But, claims Siewert, one subject, the self-cueing
blindsighter, lacks something. That something is phenomenal consciousness.

Siewert then argues that if a theory must deny the coherence or
possibility of his thought experiment, the theory neglects phenomenal
consciousness. The rejection of the scenario posited by the thought
experiment collapses the distinctly phenomenal aspects of consciousness
into mere behavioral capacities, capacities that arguably can
be exercised without the presence of phenomenal consciousness.
This deflates or neglects what Siewert sees as the most important
aspect of our conscious lives, that aspect that we know in a distinctly
first-personal manner. Siewert claims that theories that identify
consciousness with abilities to perform various perceptual discriminations
or judgments, as well as theories that identify consciousness
with forms of higher-order awareness all must reject the thought
experiment, and so neglect phenomenal consciousness.

Having exposed the alleged neglecters of phenomenal consciousness,
Siewert goes on to stress the significance of phenomenal consciousness
in our lives. He argues that phenomenal consciousness is inherently
"intentional," or about the world, because conscious
subject can be assessed for accuracy or truth in terms of what
their phenomenally conscious states are about. Furthermore, Siewert
argues that in addition to mental imagery, nonimagistic thoughts
have a phenomenal feel and can differ in their phenomenal character.
Siewert ends the book by pointing out that we would sorely miss
phenomenal consciousness if we were deprived of it, so much so
that we might prefer death to the "zombiehood" that
would follow removal of our phenomenal lives.

Siewert's book is thought provoking, but the style of the writing
makes it at times difficult to follow. There are paragraphs that
require reading and rereading by those well-versed in the consciousness
literature, so the work may not prove particularly accessible
to the lay reader. Furthermore, the central thought experiment
designed to show that many theories neglect phenomenal consciousness
is flawed. The additional considerations that are added to the
real blindsight case in order to engage specific theories of consciousness
become progressively more dubious, and in the end the argument
collapses into the claim that we can simply imagine identical
beings, one that is phenomenally consciousness and one that is
not. This is the shopworn "zombie argument," and it
is very controversial whether conceiving of phenomenal zombies
demonstrates anything that threatens empirical investigations
of consciousness. Though Siewert is undoubtedly correct that,
all things being equal, we should respect the deliverances of
our first-person access to our minds, and that we should work
to adequately explain phenomenal consciousness, he has not established
that the theories he attacks have neglected what is significant
about consciousness.